The Internet provides unprecedented consumer access to high quality health information, and progressively serves as a mediator of health education, decision making and management. The evolving healthcare system increasingly necessitates that health consumers play a more active role in managing their health. However, there are numerous barriers that preclude health consumers from fully benefiting from the range of technology- based consumer health applications. In recent years, health literacy has emerged as a useful predictor to differentiate between those consumers who are more or less likely to benefit from these applications. Although the scope of health literacy is considerable, other literacies are also critical for productive use of Internet- mediated health technologies. eHealth literacy encompasses the set of knowledge and skills that allow consumers to fully engage in and benefit from eHealth tools. The overall objective of this study is to develop a set of analytic tools based on an eHealth literacy framework and apply it to a consumer health portal in view to characterize the complexity and challenges consumers are likely to confront in using the various information resources and tools offered by the system. Towards that end, we are partnering with a "state of the art" web portal, ConsumerReportsHealth.org. The site aims to help consumers make the best healthcare decisions based on the best available research evidence. The first goal is to establish the reliability and validity of the framework and we are proposing to undertake a set of formative research activities including inter-rater reliability and predictive validity studies. We have developed a set of cognitive task analytic methods for evaluating the eHealth literacy complexity of tasks on a given site. We propose to analyze 20 tasks of varying levels of complexity on the ConsumerReportsHealth.org site. The tasks include health information seeking, decision-making (e.g., weighing treatment options), and rating (hospitals and doctors) tasks. We will also apply two automated diagnostic tools: a readability assessment metric, which integrates linguistic features of a document to determine its level of readability, and a vocabulary complexity analysis tool, which signals which health terms in a document are unlikely to be understood by a health consumer. On the basis of our analysis of complexity, we will select 10 tasks of 3 levels of complexity to be used in a cognitive study with health consumers. We will conduct cognitive studies in which 2 cohorts of 20 subjects (40) are asked to perform the set of 10 tasks identified above. The first cohort will be drawn from paid subscribers to ConsumerReportsHealth.org and are likely to be more educated and have higher levels of computer literacy than the second cohort who will be drawn from Union Settlement Association, a social service and community center in East Harlem. Institutional Review Board will be sought at the two sites and at Columbia University. A primary strength of this proposal is that we are addressing an issue of considerable and growing importance using a theoretically-grounded framework that greatly expands the scope of eHealth literacy assessment.